Vertical feedwater heater drain coolers



July 2, 1968 G. P. KOTELEWSKY VERTICAL FEEDWATER HEATER DRAIN COOLERS 2Sheets-Sheet 2 Filed Dec. 16, 1965 GEORGE P. KOTELEWS KY $MJ N UnitedStates Patent 3,390,722 VERTICAL FEEDWATER HEATER DRAIN COOLERS GeorgeP. Kotelewsky, Belleville, N.J., assignor to Worthington Corporation,Harrison, NJ, a corporation of Delaware Filed Dec. 16, 1965, Ser. No.514,275 1 Claim (Cl. 165-113) ABSTRACT OF THE DISCLOSURE A verticalfeedwater heater adaptable for two or more pass operation, having aconstruction which utilizes the pressure of steam entering the outershell of the feed Water heater to force condensate from the outer shellinto and through a drain water cooler. The condensate passing throughthe cooler is cooled in two separate zones prior to its discharge fromthe feedwater heater. The forcing of condensate from the outer shellinto the drain water cooler increase the heat transfer effectiveness ofthe feedwater heater.

This invention relates to new and improved drain coolers for use invertical feedwater heaters.

A significant problem in the operation of the vertical feedwater heatersof the prior art, which employ drain coolers of conventional design,resides in the flooding of not insubstantial portions of the totalavailable heat exchange surface areas of the heat exchange tubes bylarge amounts of condensate which accumulate in the lower portion of theouter shell adjacent the said drain coolers. Thus, the overall heatexchange tube surface area available for heat exchange duty is reducedto a correspondingly not insubstantial degree, and the overall heatexchange capacity of the vertical feedwater heater similarly reduced. Itis, accordingly, a primary object of this invention to provide new andimproved drain coolers, for use in vertical feedwater heaters, whichsubstantially eliminate the problem of flooded, and accordingly wasted,heat exchange surface areas of the heat exchange tubes to result invertical feedwater heaters of significantly increased heat exchangecapacity without requiring any increase in the total available heatexchange surface areas of the heat exchange tubes.

Another object of this invention is the provision of new and improveddrain coolers as above which result in vertical feedwater heaters ofsignificantly increased heat exchange capacity without requiring anyincrease whatever in the overall size thereof.

Another object of this invention is the provision of new and improveddrain coolers as above which are equally adaptable for use in verticalfeedwater heaters of two or four pass design and provide, in both cases,for

the efficient transfer of heat from the condensate to the feedwaterwithin the said drain coolers.

A further object of this invention is the provision of new and improveddrain coolers as above which are of decidedly uncomplicated design andconstruction, and which require the use of only relatively inexpensive,and readily available materials of proven dependability in theconstruction thereof, whereby the costs of fabrication, installation andmaintenance thereof, and of the vertical feedwater heaters in which thesame are utilized, are minimized, and long periods of satisfactoryoperation thereof assured.

, The above and other objects and advantages of my invention arebelieved made clear by the following detailed description thereof takenin conjunction with the accompanying drawings wherein;

FIGURE 1 is a vertical cross-sectional view of a ver-' "ice ticalfeedwater heater constructed in accordance with the teachings of theprior art;

FIGURE 2 is a vertical cross-sectional view of a two pass, verticalfeedwater heater constructed in accordance with a first embodiment of myinvention;

FIGURE 3 is a cross-sectional view taken along line 3-3 in FIGURE 2;

FIGURE 4 is a cross-sectional view taken along line 44 in FIGURE 3;

FIGURE 5 is a cross-sectional view of a second embodiment of myinvention;

FIGURE 6 is a cross-sectional view taken along line 6-6 in FIGURE 5; i

FIGURE 7 is a cross-sectional view taken along line 7--7 in FIGURE 6;and

FIGURE 8 is a cross-sectional view taken along line 88 in FIGURE 6.

Referring now to the drawings, a two pass, vertical feedwater heater ofa design representative of the teachings of the prior art is indicatedgenerally at 10, and comprises a shell 12 with a feedwater manifold 14formed at the lower extremity thereof and separated therefrom by a tubesheet 1d extending thereacross as shown. A baffie plate 13 extendsacross the interior of the feedwater manifold '14 to devide the latterinto a feedwater inlet chamber 20 and a feedwater outlet chamber 22. Aplurality of heat exchange tubes 24 are supported from the tube sheet 16and extend therefrom through the interior of the shell 12, with theinlet end of each of the said cooling tubes being in fluid flowcommunication with the feedwater inlet chamber 20, and the outlet end ofeach of the said tubes being in fluid flow communication with thefeedwater outlet chamber 22.

A drain cooler 26 is formed within the shell 12 by a verticallyextending baffle plate 28 which is supported from the tube sheet 16, anda plurality of baflles 30 which are supported in the depictedalternating manner from the walls of the said baffle plate and shell,respectively. A steam inlet 29 is provided in the upper portion of theshell 12, and a drain outlet 32 is provided in the lower portion of thesaid shell adjacent the tube sheet 16. Thus, feedwater under suitablepressure from any convenient source thereof may be supplied to thefeedwater inlet chamber 20, flow therefrom through the interior of theouter shell 12 in first and second passes through the heat exchangetubes 24 as indicated 'by the arrows 34 and 36, respectively, to thefeedwater outlet chamber 22. Concurrently therewith, steam at suitabletemperature and pressure, from any convenient source thereof, may beintroduced to the interior of the outer shell 12 through the steam inlet29, flow into contact with the respective surfaces of the heat exchangetubes 24 through which the feedwater is flowing, and be condensedthereby, and collect as drain water, the surface of which is indicatedat 38, in the lower portion of the outer shell 12 for the flow thereofthrough the drain cooler 26, as indicated by the arrow 40, from theouter shell 12 through the drain water outlet 32. Thus, although a goodheat exchange relationship is provided by the countercurrent flow of thefeedwater and drain water through the baflled interior of the draincooler 26, to result in initial heating of the said feedwater, a deadspace of stagnated drain water, as indicated at 40, results whereby thecondensing surfaces of the plurality of heat exchange tubes 24 whichextend through the said pool of stagnated drain water, are completelywasted and the heat exchange efficiency of the second feedwater passreduced accordingly.

An obvious, and currently widely utilized manner of offsetting thisreduction in heat exchange efliciency is to increase the length of theheat exchange tubes to provide the required tu'be condensing surfacearea above the level of the condensed drain water which has collected inthe lower portion of the outer shell 12. This increase in the length ofthe respective heat exchange tubes 24 results not only in a significantincrease in the space required for the installation of the verticalfeedwater heater, but also, in a significant increase in the cost offabrication of the said feedwater heater due to the greater amounts ofmaterial required for the construction of the longer heat exchange tubes24, andthe correspondingly longer outer shell 12. Thus is believed madeclear that an increase in the length of the said tubes does notrepresent a satisfactory solution to the problem of wasted, cooling tubesurface condensing area.

A satisfactory solution to the problem of washed heat exchange tubesurface area is, however, believed provided by applicants inventionwhich, as seen in the embodiment of FIGURES 2, 3 and 4, takes the formof a two pass, vertical feedwater heater 11 comprising a generallysimilarly arranged combination of correspondingly identified, verticalfeedwater heater elements. In addition, the vertical feedwater heater 11of the embodiment of FIGURES 2, 3 and 4, comprises a bafile plate 42which extends in the depicted, generally radial manner, as best seen inFIGURE 2, from the interior wall of the outer shell 12 to the baffleplate 28 to thereby divide the interior of the drain cooler 26 intofirst and second chambers which are identified respectively as A and B.

A cover plate 44 extends as shown over the drain cooler 26 into contactwith theadjacent upper extremity of the baffle plate 28 to thus seal thedrain cooler from the remainder of the interior of the outer shell 12and prevent the flow of condensed drain water from the former to thelatter. A drain water inlet opening 46 is provided adjacent the lowerextremity of the baffle plate 28 to permit the flow of drain water intothe chamber A of the drain cooler 26, and a drain water transfer opening48 is provided by the termination of the bafiie plate 52 short of theunder surface of the cover plate 44 to permit the how of drain waterfrom the chamber A of the drain cooler to the chamber B thereof.

In the embodiment of FIGURES 2, 3 and 4, the drain water outlet 32,(FIGURE 4) extends as shown from the cooler chamber B to the exterior ofthe vertical feedwater heater 11, whereby may be readily understood themanner in which the condensed drain water, as again indicated at 38 inFIGURE 3, may be collected in the lower portion of the outer shell 12outside of the drain cooler 26, be forced by the pressure of the steamwithin the said outer shell to flow into chamber A of drain cooler 26through drain Water inlet opening 46 and substantially fill the saidchamber, then flow from chamber A to chamber B through drain watertransfer opening 48, and finally flow from the latter chamber to theexterior of the vertical feedwater heater through the drain water outlet32 provided therefor in the exterior wall of the chamber B.

The pressure of the steam Within the outer shell 12, the amount of drainwater condensed per unit time, the total volume of the drain cooler 26,and the respective sizes of the drain water inlet opening 46, the drainwater transfer opening 48, and the drain water outlet 32, arepredetermined to both maintain the condensed drain water, within theouter shell 12 but without the drain water cooler 26, at the relativelylow level thereof depicted in FIGURE 3, and to cause the said condenseddrain water to substantially fill the interior of the said drain watercooler once steady state operational conditions have been reached by thefeedwater heater 11.

Thus, the vertical feedwater heater 11. of FIGURES 2, 3 and 4 willprovide parallel how of the drain water and the feedwater which flowconcurrently through chamber A of the drain water cooler 26, and willprovide for counterflow of the said drain water and feedwater which flowconcurrently through the interior of chamber B, to result in theefficient transfer of heat between the 4 said drain water and feedwater,and resultant preheating of the latter.

It has been determined by the actual taking of test data, andcalculations based thereon, that the construction of FIGURES 2, 3 and 4provides for approximately 70% of the total drain water cooling due tothe parallel flow of the drain Water and feedwater through chamber A ofthe drain water cooler 26, and approximately of the total drain watercooling due to the counterflow of the drain water and feedwater throughchamber B of the said drain water cooler. In addition, it has beendetermined that the weighted MTD of chambers A and B comprises 91% to96% of the weighted MTD of the single chamber, one counterflow passdrain cooler arrangement of the prior art as depicted in FIGURE 1 anddescribed in detail hereinabove.

Of additional significance, however, is the fact that the level of thecondensed drain water within the interior of outer shell 12, but withoutthe drain cooler 26 of the feedwater heater 11, is substantiallylowered, as made clear by but a brief comparison of FIGURES l and 3,whereby the amount of dead space, and accordingly wasted'condensingsurface area of the heat exchange tubes 24, caused by the pool ofstagnated drain water as indicated at 40 in FIGURE 1, is alsosubstantially reduced to provide for a vertical feedwater heater 11 ofsignificantly increased operational efficiency without attendantincrease in feedwater heater size and cost of fabrication. v

A four pass, vertical feedwater heater constructed in accordance withthe teachings of applicants invention is represented at 13 in theembodiment of FIGURES 5, 6 and 7, and, as seen therein, again comprisesa. generally similarly arranged combination of correspondinglyidentified, feedwater heater components. In this embodiment, however,the interior of the feedwater manifold 14 is divided, as best see-n inFIGURE 8, by baffie plates and 52 into a feedwater inlet chamber 54 withan inlet pipe 55 leading thereto, a feedwater transfer chamber 56, and afeedwater outlet chamber 58 with an outlet pipe 59 leading therefrom,respectively. This is made possible the flow of the feedwater throughfour passes during the traverse thereof of the vertical feedwater heater13, with the said feedwater flowing from the feedwater inlet chamber 54upwardly through those of the heat exchange tubes 24 in communicationwith the said inlet chamber for the first feedwater pass, downwardlythrough the same said heat exchange tubes into the feedwater transferchamber 56 for the second feedwater pass, upwardly through the remainderof the heat exchange tubes 24 which are in fluid flow communcation withthe said feed- Water transfer chamber for the third feedwater pass, anddownwardly through the said heat exchange tubes into feedwater outletchamber 58 for the fourth feedwater pass.

In this embodiment, the plurality of heat exchange tubes 2.4 areoriented differently relative to the chambers A and B of the draincooler 26, with only the heat exchange tubes which function to conveythe feedwater through the first and second passes thereof being arrangedto pass through the drain cooler as made clear by FIGURE 7. The drainwater flow through the said drain cooler is thesame in this embodimentas it is in the embodiment of FIGURES 2, 3 and 4. Thus, the said drainwater will again collect at a relatively low level, within the outershell 12 but without the said drain cooler, as indicated at 38, beforced by the pressure of the steam within the said outer shell to howinto drain cooler chamher A through drain water inlet opening 46extending there-between, then flow from drain cooler chamber A to draincooler chamber B through drain water transfer opening 48 extendingtherebetween, and finally flow from drain cooler chamber B to theexterior of the feedwater heater 13 through drain water outlet 32. As aresult, the said drain water will again function to substantially fillthe interior of the drain cooler 26 once steady state operation has beenreached.

By this construction, counterfiow of the drain water and feedwater,during the portions of both the first and second feedwater passes inwhich the feedwater passes through the drain cooler, is provided, withthe feedwater flowing upwardly through drain cooler chamber B during thefirst pass thereof concurrently with the downward flow of drain waterthrough the said chamber, and the feedwater flowing downwardly throughdrain cooler chamber A during the second pass thereof concurrently withthe upward flow of the drain water through drain cooler chamber A. Thusis believed made clearly whereby the embodiment of FIGURES 5, 6 and 7provide for the same significant saving in cooling t-ube condensersurface area in a four pass, vertical feedwater heater as does theembodiment of FIGURES 2, 3 and 4 in a two pass, vertical feedwaterheater to again provide for significantly increased operationalefiiciency without attendant increase in the size and cost offabrication of the said feedwater heater.

The actual taking of test data and calculations based thereon haveestablished that the application of the teachings of applicantsinvention to the construction of vertical feedwater heaters makespossible a reduction in the required, overall condensing surface area ofthe heat ex change tubes ranging from 3 /2% to 20%, whereby the amountof such condensing surface area required by vertical feedwater heatersof similar design of the prior art may be reduced by amounts within thissame range without attendant reduction in the heat exchange capacity ofthe said vertical feedwater heaters.

Thus, for example, the application of the teachings of applicantsinvention to a vertical feedwater heater of the prior art which requires15,000 square feet of heat exchange tube condensing surface area toprovide a required heat exchange capacity, can result in the saving ofroughly 500 to 3,000 square feet of this tube condensing surface area toenable significant reduction in the size and cost of fabrication of thesaid vertical feedwater heater. In this regard, it is believed ofinterest to note that, in cases where stainless steel heat exchangetubes are requiredthe cost thereof being roughly $10 per square foot ofheat exchange tube condensing surface areathe saving of 500 to 3,000square feet of heat exchange tube condensing surface area may readily beseen to result in a reduction in the cost of fabrication of the saidvertical feedwater heater ranging from $5,000 to $30,000 per unit. Forapplications in which copper heat exchange tubes are satisfactory-thecost thereof being roughly $6 per square foot of condensing surfaceareacost reductions in the range of $3,000 to $18,000 per verticalfeedwater heater unit are made possible.

It is to be understood that these cost reduction figures do not includethe additional cost reductions made possible by the attendant reductionin the length of the outer .shell 12, nor do they include the costreductions made possible by the fact that the reduced size of thevertical feedwater heater enables the same to take up less space, whichis, in many applications, at a decided cost premium.

It will be understood that the invention is not to be limited to thespecific construction or arrangement of parts shownbut that they may bewidely modified within the invention defined by the claim.

Drain cooler shrouding may, if desired, be provided in both of thehereinabove-disclosed embodiments of applicants invention inconventional, non-illustrated, manner to make possible the convenientremoval of the major portion of the feedwater heater outer shell, in amanner well known to those skilled in this art, to enable the readyinspection and/or maintenance of the internal components of therespective feedwater heaters of the said embodiments.

What is claimed is:

1. In a vertical feedwater heater including an outer shell, a tube sheetin the lower portion of the outer shell, a plurality of heat exchangetubes extending from said tube sheet within said outer shell, means toflow feedwater in a plurality of passes through said heat exchange tubesincluding water box means associated with said tube sheet and saidplurality of heat exchange tubes, partition means separating said waterbox means into at least first and second compartments, and feedwaterinlet means in said second compartment, and means to introduce steamunder pressure to said outer shell and condense said steam throughcontact with said heat exchange tubes, the improvement comprising:

means forming a closed drain cooler extending generally vertically inthe lower portion of said outer shell, said drain cooler occupying lessthan the total area of said lower shell portion;

generally vertical baffle plate means dividing said drain cooler intofirst and second zones;

at least one of said heat exchange tubes includes first and secondspaced portions thereof which extend respectively through said first andsecond drain cooler zones;

at least one other of said heat exchange tubes includes spaced portionsthereof adjacent said tube sheet which do not extend through either ofsaid drain cooler zones;

outlet means in the lower portion of said second drain cooler zone forremoving drain liquid therefrom;

passage means in the upper portion of the means dividing said draincooler zones to allow drain liquid to flow from said first drain coolerzone to said second drain cooler zone;

inlet means in the lower portion of said first drain cooler zonecommunicating said remaining area of said lower shell portion with saidfirst drain cooler zone to allow condensate which collects in theremaining area of said lower shell portion to enter said first draincooler zone and, through the effect of the steam pressure in the outershell, flow upwardly in said first drain cooler zone and then throughsaid passage means to said second drain cooler zone whereby, largeaccumulations of condensate in said outer shell are prevented; and

each of said heat exchange tubes including first and second spacedportions extending respectively through said first and second draincooler zones is connected to said tube sheet so that said second spacedportion of said heat exchange tube in said second drain cooler zone isin fluid flow communication with said second water box compartment andsaid first spaced portion of said heat exchange tube in said first draincooler zone is in fluid flow communication with said first water boxcompartment, whereby the flow of feedwater through said second spacedportion of said heat exchange tubes is upward and fiow through saidfirst spaced portion is downward thereby producing countercurrent flowbetween the flow of feedwater in those portions of the heat exchangetubes which extend through said drain cooler.

References Cited UNITED STATES PATENTS ROBERT A. OLEARY, PrimaryExaminer.

A. W. DAVIS, Assistant Examiner.

